Must declare function prototype in C? [duplicate]

Answer 1

Select ‘Options’ menu and then select ‘Compiler | C++ Options’. In the dialog box that pops up, select ‘CPP always’ in the ‘Use C++ Compiler’ options. Again select ‘Options’ menu and then select ‘Environment | Editor’. Make sure that the default extension is ‘C’ rather than ‘CPP’.

Answer 2

Function prototype is not mandatory according to the C99 standard.

Answer 3

In C, if we do not declare a function prototype and use the function definition, there is no problem and the program compiles and generates the output if the return type of the function is "integer". In all other conditions the compiler error appears. The reason is, if we call a function and do not declare a function prototype then the compiler generates a prototype which returns an integer and it searches for the similar function definition. if the function prototype matches then it compiles successfully. If the return type is not integer then the function prototypes do not match and it generates an error. So it is better to declare function prototype in the header files.

Answer 4

C allows functions to be called even though they have not previously been declared, but I strongly recommend you to declare a prototype for all functions before using them so that the compiler can save you if you use the wrong arguments.